1. Field of the Invention
The present invention relates to a friction pad for a disc brake and more particularly to an improvement for a friction pad used for a disc brake in which a braking torque generated on an outer pad is supported by a stationary portion of the vehicle via a caliper.
2. Description of the Prior Art
As the conventional disc brake, there has been known such a disc brake that a braking torque generated on an outer pad is supported by a stationary portion of the vehicle via a caliper and a braking torque generated on an inner pad is supported by a support member (for example, Japanese Utility Model Publication No. Sho. 62-130233). In this disc brake, the caliper straddling a rotor is movably supported by a support member which is attached to the vehicle body in such a manner that the caliper is movable in an axial direction of the rotor axis via a pair of guide pins, and the inner pad is brought into pressure contact with the rotor by a hydraulic pressure cylinder device disposed on the inner side of the caliper. By the reaction force, the caliper is moved, so that a caliper pawl on the outer side brings the outer pad into pressure contact with the rotor. In this case, the outer pad is fitted to the caliper pawl via a concave and convex fitting structure and the braking torque generated on the outer pad is transmitted to the caliper pawl.
In the aforementioned disc brake, the braking torque generated on the inner pad is supported by the support member, and the braking torque generated on the outer pad is transmitted to a rotor run-in side guide pin via the caliper pawl so as to be supported by the vehicle body. Accordingly, a protrusion which engages with a torque transmission hole formed in the caliper pawl is formed in a back plate of the outer pad in the conventional brake.
The aforementioned protrusion is formed by press-drawing. For example, as disclosed in the above Japanese Utility Model Publication No. Sho. 62-130233, a recess is worked on a front surface on which a lining is attached of the back plate, thereby the protrusion is formed on a back surface of the back plate, and the back plate is attached to the caliper via the back surface.
However, when the protrusion is formed on the back plate, the press-drawing is performed from the side of the front surface on which a lining is attached. Therefore, a problem occurs in that the thickness of the back plate at a base portion of the protrusion is decreased because it is necessary to secure enough height for the protrusion that the pad is supported securely. So the height of the protrusion has been limited in view of the thickness of the base portion of the back plate. Accordingly, it has been necessary to reinforce the engagement of the outer pad with the torque transmission hole by a clip provided separately. For this reason, problems such as encreased of parts and complicated structure of the back plate have been encountered.